1. Field of the Invention
The present invention relates generally to the booting/rebooting of embedded systems. More particularly, the present invention is directed towards booting/rebooting a plurality of embedded system modules within an optical node of an optical network.
2. Description of Background Art
Wavelength division multiplexed (WDM) optical networks are of interest for optical communication networks, such as long-haul networks and metro area networks. A WDM network typically includes several data channels, with each data channel having a corresponding optical wavelength. A dense wavelength division multiplexed (WDM) optical network typically has twenty or more channels.
FIG. 1 shows an example of a DWDM optical network 100 having a ring topology, although it will be understood that a DWDM optical network may assume a variety of different topologies. A DWDM optical network typically includes two or more optical nodes 105 linked by optical fibers 110 into an optical network 100. Each optical node 105 commonly included elements for passing channels on to downstream nodes using optical amplifiers or optical regenerator elements. Additionally, each optical node 105 is typically coupled to a local tributary network coupled to optical network 100 (not shown in FIG. 1) and includes elements for adding/dropping channels to and from the tributary network.
FIG. 2 is a functional block diagram of an exemplary DWDM optical node 200 developed by ONI Systems Corp. of San Jose, Calif. Optical node 200 includes at least one input port 205 for receiving an optical data stream and at least one output port 210 for communicating an optical data stream with a downstream node. A service interface 215 permits data to be coupled to/from a local tributary network. Optical node 200 may be conceptually divided into functional blocks of elements. Transport section 260 has interfaces for receiving a line-side optical data stream from an upstream node and communicating a line-side optical data stream to a downstream node. Some of the functions that transport section 260 may provide include receiving/transmitting an optical supervisory channel; dividing the received optical signals into working, protection, and supervisory channels; providing protection switching, or amplifying optical signals to boost their signal strength. A multiplex section 270 may include a multi-stage optical multiplexer. The multiplex section 270 aggregates optical signals from the tributary section 280 into the line-side DWDM format. Multiplex section 270 also splits received line-side signals into the individual channels used by a tributary section 280. Tributary section 280 may include transponders to bi-directionally convert optical signals from tributary equipment to the specific frequencies used on the optical transmission line. A common control section 290 provides software administration and control of the node and may include a configuration database and a central control processor.
A DWDM optical node 200 includes a substantial number of opto-electronic and electrical components. Consequently, each major functional block 260, 270, 280, and 290 of an optical node 200 may be further divided into rack-mountable modules (commonly referred to as “circuit packs”). Referring to FIG. 3, a rack 300 includes several shelves 305, with each shelf having several slots for holding a circuit pack 308. Each circuit pack 308 includes one or more electrical components and one or more opto-electronic components mounted to a supporting substrate, such as a printed circuit board. A circuit pack 308 may also include a mechanical sub-structure to provide mechanical strength, provide an electromagnetic interference shield, and facilitate air flow through the rack. Examples of circuit packs are circuit packs containing optical multiplex/demultiplex elements, circuit packs containing optical amplifiers, circuit packs having optical transceivers, and circuit packs having optical switching elements (e.g., a ring switch module). The circuit packs 308 may be coupled to an electronic data bus to permit the circuit packs to communicate electrical data signals with each other. For example, referring to FIG. 3, the node may include one or more local area networks 300 (e.g., an Ethernet back-plane having a databus and hubs) to provide a back-plane data link for circuit packs 308 located in different shelves 305 of a rack 300. A circuit pack 308 may also include one or more optical ports (not shown in FIG. 3) to permit opto-electronic elements of the circuit packs to be coupled together with optical couplers (e.g., segments of an optical fiber).
The use of standardized circuit packs 308 to implement the functional blocks of an optical node 200 provides many commercial advantages, such as the ability to repair or upgrade optical node 200 by swapping circuit packs. However, a DWDM network may require a substantial number of circuit packs 308 in each node. This may lead to a variety of booting/rebooting problems for circuit packs having a microprocessor requiring a central data resource from a processor module 318 to boot/reboot. One problem observed by ONI Systems Corp. of San Jose, Calif. is that during booting/rebooting of node 200 a congestion/overload condition may occur due to the large initial message traffic between circuit packs 300 and the central processor 318 of the control section. This results in an undesirable delay when the modules are started in a boot/reboot process. The delay tends to increase as the number of modules is increased, is exacerbated by a slow bus/hub speed, and also depends upon the speed of the central processor. This delay in the booting/rebooting process may be unacceptable for many applications. Moreover, since both congestion and overloading delays tend to increase rapidly above a threshold level of message traffic, the delays may increase dramatically as the number of modules is increased above a threshold number. Conventional solutions to congestion and overloading, such as increasing the bus speed and the speed of the central processor, would significantly increase the cost of optical node 200.
Therefore, there is a need for a new system and method for starting/restarting the circuit packs in an optical node.